I haven't both in my interactions with Thais and from what I've seen in popular culture, at least not in 2025. Plenty of French kissing scenes either explicit or intimated in gay and straight Thai films, TV series, porn, literature and comics. Safer sex campaigns address the issue of French kissing which means it is something that people do. Some sex workers, on the other hand, may be reluctant to French kiss for various reasons, for example, it's a deeply intimate act reserved for partners, hygiene, perceived fear of contracting certain diseases, etc. Bear in mind that sex workers see multiple customers of unknown backgrounds in a month and while the risk of contracting an STI through kissing may be low, it is much higher for them and they don't want to pass it on to their wives, boyfriends or other customers.