A Thai girl, or any feminine girl without a strong religion to contain her actions is not going to be
with you exclusively unless she loves you. She is going to be open for flirting or more by other guys if she's not in love passionately. Whether she is in a relationship or not.
But if she does love you, she will probably utterly ignore any message or attempt any other guy will make. Or at the most talk with other guys like friends and stop contact if they start to make a move on her.
Try not to get all butt-hurt about some "playgirls" in here if you're looking for a relationship. Even the playgirls reject far more interesting offers than you ever would if you got the same amount of offers as them.
I believe that in order to be able to keep a girl, your dating value has to be higher than hers.
And by "keep" I mean keeping her in love and faithful. Almost anyone can marry a cute thai girl with money but that girl will be fucking around if that's all she wanted from you.
Here you have far higher dating value than back home. That is why foreigners do so well in Thailand compared to their home countries.
You can be dating and fucking a girl for a while even if she's hotter than you, but she will eventually move on, often sooner rather than later unless you manage to ramp up your dating value while you're seeing her.
Because when you first meet a hot girl she's already probably dating others or gets a lot of offers from guys. You can temporarily display higher value than what you truly have and hook up with 10s even with just good game but eventually she will know that she's the hotter one and wants a new "good enough" guy or
to find a hotter guy than you. Make no mistake. Bangkok is a very competitive place to hook up with the hottest girls. There's a lot of handsome foreigner playboys here. Many of them even live here.