What are the key tips for successfully applying for a visa in Thailand?

Tutorial.

Before applying, check the web for ppl who successfully applied from the exact same situation as yours. often they share files they provided. use them.

the application site is tricky. you can't change it, you can't trick it.

so before you finally submit, you check each and every letter of your data.

the passport scan function is the direct way to being rejected. scan, and then check and mostly edit each field, so they match your passport.

deliver what they ask for. not more, not less.

have more money on your account than the equivalent of 500k baht. exchange rates change, and the process can last longer.

you can't appeal, you can't "talk to somebody". so be diligent, don't mess around. each pdf can only be one file. if you have more pages, ask google how to connect them.

ignore facebook groups. the amount of false and guessed info is tremendous.

finally: different nationalities have different levels of requirements. different countries may ask for different documents. so think twice where you want to apply.