There are many reasons why fans really support this shipping. This took a lot of work, i had a review on each episode i watched lol. I have did all of these in one night i tryed very hard looking for a lot of these hints and moments. If i missed some hints that i dont know of, please give me a message in www.youtube.com/EliteLugia
Here are the hints
Hoen League Season
Ep: Get The Show On The Road
Ash destroys May's Bike accidentally, she gets mad and tells him off while he is in the pokemon center.
She quietly opens the door, she watches Ash and Pikachu resting contently together, and she forgives him without telling him. Later on, May figuratively talks Ash into letting her travel with him. Once he says she could come along, May strikes a pose by the camera and yells, "YES!" to show her enthusiasm to the audience. This shows that May likes ash.
Ep: A Ruin with a view
Ash decides to become May's mentor for the very first time, teaching her how to capture and battle with Pokémon. The two have dinner together in a Pokémon Center, and when Ash wants to find out about the gym leader in petalburg, May frantically pulls him by the arm to prevent him from finding out. It would appear that she was far more content with traveling with Ash alone before revisiting her family.
Ep: A Stairway to Devon
When Ash and May discover that a team aqua intruder is in the building and Max could be in potential danger, she clasps her hands and asks Ash for reassurance and support. Once Ash comforts her, she is relieved. This is the first of many scenes where May continually looks toward Ash for support and reassurance.
Ep: Brave the Wave
On Dewford Island, May decides to strip into a bikini right on the beach. However, instead of just running down to the shore to take a swim, she purposely poses in her bikini in front of Ash and her brother and asks what they think. Ash appears to be embarrassed by the situation.
Ep: Win, Lose or Drew!
After May lost her first pokemon contest , Ash takes the blame for her loss. He says, "It’s my fault. I wish I’d spent more time with May, teaching her." Later, May is crying backstage as Ash tries unsuccessfully to cheer her up.
Ep: A Togepi Mirage!
When Brock asks Misty and Ash to go save Togepi, May says she will go too. This may have been because she did not like the idea of Misty being alone with Ash, even though Princess Sara went with them.
Ep: All Torkoal, no play!
When May is clutching Torchic in her arms, the ground underneath her collapses and she falls into a chasm. Luckily, she grabs ahold of a branch that was sticking out of the wall. When May frantically calls for help, Ash steps up to rescue her. He tied a rope around his body as Max and Brock lower him down, where he grabs ahold of May's arm and reassures her that everything will be alright. Further expanding on the heroism, where May thanks Ash dearly for saving her life.
Ep: Go Go Ludicolo
When confronted by Max whether she wants Ash to win over her Dad, Norman of the Petalburg Gym, May gives flustered responses. While Max is quick to make up his mind and cheer for his father, May on the other hand sides with Ash. Max yells, "What, how can you want Ash to win over our Dad?" to which May blushes nervously and says, "Well I want Dad to win... but I don't want Ash to lose!"
May's choice was made up from the beginning to cheer for Ash over her father, and each time Max confronts her about it, she blushes nervously and doesn't want to give him a clear answer.
Ep: The Bicker The Better
Many of you avdanceshippers may know this hint already, but its when Ash and May are confronted by Oscar and Andi, a young couple who are obsessed with the idea of love and romance.
When Oscar and Andi call Ash and May a "happy couple," the two of them quickly deny it and turn their backs to one another, crossing their arms. Ash says sarcastically, "That's a laugh!" and May adds, "Hardy har har!". Oscar and Andi do not stop there, and continue to call them a couple. Ash and May scream, "We're not a couple!" in unison, with the same body language, followed by, "And we're not happy either!" in the same tone in which Oscar and Andi state that they 'both answered together' further causing tensions between the two.
Ep: Grass Hysteria
May is lost in the forbidden land of the Grass Pokémon, Ash once again steps in to save her. After his Tarzan-esque entrance to save May from the fierce and threatening Grass Pokémon that were about to attack her, he grabs her by the hand and runs with her to clear a path to safety. Ash and May continue to hold hands as they are running away from the menacing Pokémon, a rare sight between them.
Ep: Hokey Poke Balls
By having Ash and Mays Bulbasaur meet each other, the two Bulbasaur show signs of liking one another, a ship that is called VineShipping. Throughout the episode, May makes several comments about how their Bulbasaur are such a great team, and how they are, "Two peas in a Poképod." Before Ash sends Bulbasaur back to Professor Oak, it pats May's Bulbasaur on the head sweetly with its vine, saying goodbye. May's Bulbasaur is impressed as Ash's Bulbasaur is sent back. Vineshipping is one of the parallels that is used to push Advanceshipping, as canon characters such as Professor Oak and Brock have said in the past that Pokémon represent the feelings of their trainers, and when two Pokémon fall in love, there is a good chance the trainers will too. This increases the chances of advanceshipping.
Ep: Cruisin' for a losin'
May is sulking on a bench outside the Contest hall because she lost her match. Ash comes alone to comfort her, cheering her up compassionately while patting her Bulbasaur on the head and sitting next to her on the bench. This is followed by a, "Thank you Ash," from May.
Ep: A Scare to Remember
Pikachu developed amnesia and joined Team Rocket. Pikachu ended up shocking Ash and, the second time it happened, May covered her face in possible concern for Ash.
Ep: The scuffle of Legends
Ash is about to hop on top of Dragonite and go with Lance to save Pikachu from its bonding with the Blue Orb and Groudon, May approaches Ash and says, "Don't do anything crazy Ash," in a sweet and very concerned tone.
Ep: Once in a Mawile
Many fans of advanceshippers have seen this too. Ash is confused about the concept of love. May teases him and says, "Spoken like a maaaaaan," in the dub while she says, "And he doesn't get it," in the original raw. As the episode continues, Ash says, "No sense in going out of your way just to make somebody like you," in which May responds, "And he still acts like a man," in the dub while in the raw, "And he reeeaaaally doesn't get it." This is the second episode where May teases Ash about love.
Ep: Let it Snow, Let it Snow, Let it Snowrunt
May holds onto Ash's hat while he is lost with Snorunt in a blizzard. May holds onto his hat during the entire search, frantically hoping to find him again, which is seen as a romantic gesture. Once they meet up again, she says, "I believe this is yours!" and kindly hands Ash back his hat.
Ep: Date Expectations
When may is about to be ran over by a Donphan using Rollout attack, Ash launches his body toward May and brings her to safety. The two fall down to the ground with his arm around her torso. This is the third time Ash has saved May from danger. In the middle of the episode, Ash and May are separated from the group. May does her expedition routine and thinks about the concept of being lost with Ash in the woods forever. This idea causes her to have little red blushes on her cheeks. During the last act of the episode, May misses her chance to catch the ferry to her final Contest. In despair, she starts to cry. Sensing her pain, Ash puts his hands on her shoulders and stares at her deeply in the eyes, giving her the courage to go on while he takes care of her little brother. This is the first time that Ash had ever put his hands on a girl in such a serious and compassionate manner.
Battle Frontier Season
Ep: The Right Place and the Right Mime
May decides that she wants to continue traveling with Ash after Hoenn ends, which compels her to travel from the Hoenn region on her own to meet up with Ash in Pallet Town. This was before she found out there were Contests in Kanto, so she decided that she wanted to be by Ash's side even if it meant not continuing her coordinator dream for the time being.
Meanwhile, May decides to leave her Bulbasaur with Ash's Bulbasaur at the lab, further following up with the concept of VineShipping over 50 episodes ago. The two Bulbasaur again show signs of liking one another, which could be used to push AdvanceShipping in the future.
Ep: Fear Factor Phony!
When May hears sounds of scary Ghost Pokémon, she frantically goes to Ash and tries to wake him up in his sleeping bag. She presses her hands desperately against his chest to wake him up, yet she didn't do the same for Brock, who could have come to her aid just as easily. A further example of May choosing Ash over anyone else when she is in fear or doubt.
Ep: On Olden Pond
As Ash is fishing, the line is being pulled into the water. To prevent him from going overboard, May quickly wraps her arms around his torso and presses her chest against his back. Ash puts on a flabbergasted expression as he feels May's chest pressed up against his back.
Ep: Off the Unbeaten Path
May falls off a rope bridge and clutches for her life. Once again she cries out for Ash several times, despite the fact that Brock is standing with Ash as well. Ash calls out May's name as he pulls her to safety, but not once does May give any gratitude toward Brock for saving her, only Ash (this does not occur in the English dub). In the English dub Ash calls out only May's name but Max was there too.
Ep: Harley Rides Again
James says to Ash that they were helping his girl (May) in the Contest.
Ep: Home is Where the Start is
All of you advanceshipper fans may have known this already. When there is only one ribbon, and they can't decide who to give the ribbon to, May looks at Ash, and Ash looks at May, and they nod at each other, and then Ash tells Sceptile to Leaf Blade the ribbon in half. This proves that sometimes Ash and May do not need to speak to each other to know what the other is thinking because they share such a close bond. Also, in Mean With Envy!, Erica and Joshua were seen in a fantasy holding a split ribbon while Vivian was referring to a couple winning a Contest. Ash and May repeated their actions when they won.
Jirachi: Wish Maker
One of the nights when May folded a tab on the wishing star, she afterward looked down to Ash who was at that time; skipping rocks across a river. The camera then goes back to May, which she has a very anxious look on her face. Because of this scene, many Advanceshippers believe that May's wish had something to do with Ash (though this was never confirmed)
All advanceshippers may have already know this, Ash tries to pick a fight with Tory Lund. In order to stop him, May throws her body on top of Ash and tells him to please stop. She places her hands on his shoulders and desperately tries to convince him to calm down. Ash is surprised with her action, and quickly says, "Sure."
Lucario and the Mystery of Mew
Ash loses his cool and gets mad at Lucario. May rushes down into the lake where Ash is standing and clutches to his arm, trying to prevent him from getting himself in trouble. May holds onto him frantically until the situation is resolved. Afterward, May follows Ash around "mothering" him, telling him to get himself dry before he catches a cold.
Pokemon Ranger and the Temple of the Sea
I have alot to say about this movie, Ash and May go swimming with Manaphy, they continuously shoot glances at each other and smile. This is accompanied by a school of Luvdisc, Pokémon thought to symbolize love.
Later when they were in the submarine, May was crying up against the submarines window because she thought she had driven away Manaphy. The camera shoots a moment over to Ash who has a deeply concerned look.
When Samiya was being flooded with water, Ash put May, Pikachu, and Manaphy in a capsule left behind by The Phantom, allowing them to survive should his plan to replace the crystal fail. May continued to pray for Ash's safety and was nearly driven to tears when she thought he wouldn't make it back. Manaphy sent May's prayers to Ash, and with these thoughts spurring him on, Ash recovered from his near-drown state and replaced the crystal, saving the Samiya.
After the Samiya is raised, May leaves the capsule, at the beginning thrilled that the temple is saved (In the Japanese language version of the movie, she acknowledges that Satoshi is the one who saved the Temple by saying "This is Satoshi's doing, isn't it?"). Her happiness, however, is quickly replaced by sadness with the fear that Ash hasn't returned. "It can't be..." she says. "No way..." Her joy returns as soon as Ash flies up out of the water and chases down Phantom and saves the abducted Manaphy.
In the manga adaption of the movie, when May and Pikachu are unsure of whether or not Ash survived trying to save the Sea Temple, she cuddles Pikachu and is tearing, but still retains hope in Ash by saying "Ash wouldn't leave us like this..."
Diamond & Pearl Season
Ep: A Full Course Tag Battle
May joins up with Ash, Brock, and Dawn in Sinnoh. Under a full moon, Ash and May both pull out their halves of the ribbon that they tied for, and hold the pieces together. May also says how the ribbon reminds her of Ash's encouragement, and how it has saved her numerous times in Johto. When Ash pulls it out, it was not even in his bag it was in his pocket so that must mean he holds it in his pocket all the time and thinks of May. look down at the pic ^^
Ep: Strategy with a Smile
Before May leaves to return to Johto, she and the rest of the group share goodbyes. She and Ash speak last, each telling the other to do their best in their respective paths. It is only when May is speaking with Ash (despite the fact she was exchanging farewells with everyone) that she holds her heart. Further indication is that when both May and Ash say their goodbyes, each of their eyes glimmer. In the anime, when a character's eyes glimmer it represents a type of passion.
Ash and Mays Simalarities
Both have a bulbasaur and Squirtle The relationship between their two Bulbasaur has extended to the point where a separate shipping has been named for them, VineShipping.
Ash has a Snorlax and May has Munchlax
Both have bug/flying type pokemon of when they first caught there very first pokemon when they were beginners, Butterfree and Beautifly.
Both like the same kind of food
Both have a fully-evolved Fire-type starter Pokémon from their home region (Charizard and Blaziken)
Both also have a fully-evolved Grass-type starter Pokémon from each other's region (Sceptile and Venusaur).