The 57 million-euro (£49 million) signing from Santos opened the scoring after only 11 minutes, nudging home a low cross from Cesc Fabregas in front of a crowd of just over 48,000.
He started in a front three with world player of the year Lionel Messi, who scored twice, and Spain forward Pedro, who hit a hat-trick.
"Friendly games like these help me to see different possibilities, variations, but clearly the idea is that he (Neymar) progresses," new Barca coach Gerardo 'Tata' Martino told a news conference.
"From the game against Santos to today he has improved.
"The link-up between the two (Messi and Neymar) is what most caught the eye. They connected well, they scored, but they also linked up well with the other players."
In-form Chilean forward Alexis Sanchez scored Barca's seventh as a second-half substitute.
Thailand's goal was netted by forward Teerasil Dangda from the penalty spot just before halftime.
Barca started with youth-team defender Frank Bagnack alongside Gerard Pique at centre back as they continue their search for solutions to help cover for the ageing and injury-prone Carles Puyol.
Earlier in the day, media reports said Barca had made an official offer for Chelsea's Brazilian defender David Luiz.
"I am in Thailand, I don't know about any negotiations that may be taking place," Martino said when asked about the interest in Luiz.
"Bagnack needs to train with us more, with the older players, and copy them. I need to see more of him but with the little time I have had with him, he has raised expectations."
Barca play another friendly, against a Malaysia XI in Kuala Lumpur, on Saturday before returning to Spain to finish their preparations for the start of the La Liga season, and their opening match at home to Levante on August 18.
Barcelona team: Valdes, Pique, Fabregas, Pedro, Messi, Neymar, Song, Adriano, Dani Alves, Sergi Roberto, Bagnack. Subs: Pinto, Xavi, Iniesta, Sergio, Bartra, Montoya, Mascherano, Alexis, Dongou and Alba.