Had better (do such-and-such) / (such-and-such) ดีกว่า
English and Thai both use the word for “better” to describe a preferred action. “You had better do your homework first.” ทำการบ้านก่อนดีกว่า
Wikipedia tells me that the English usage is as a modal auxiliary verb. Just don’t get carried away: the two aren’t exactly similar. I’m not sure why, but you can’t say “The bus had better get here soon,” as รถเมล์มาแล้วดีกว่า–it’s nonsensical. (Consider รถเมล์ต้องมาเดี๋ยวนี้.) So I think it’s best say ดีกว่า when something would literally be “more good.”
Some may say that this is too common in all languages to deserve special attention; but my objective is to expose ways that good English speakers can become good Thai speakers (and, wherever possible, vice versa). Like Krav Maga, the idea is to exploit natural reflexes, except that instead of whooping ass, the idea is to communicate better.