So the 800,000k must have been in a Thai bank for at least 3 months before applying then go to immigration office and check what others things you need
if you don't have any proof that you will leave Thailand or you have current visa you will not enter Thailand because they think that you are going to stay in Thailand.
so you need the return fight because you want get in Thailand because your visa wants be approved so as you are saying the immigration officer's are there for nothing just to look at your passport
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