Is that going to be standard procedure at Chiang Mai from now on? Chiang Mai was my first port of entry on my DTV in November and I didn't get questioned. Hoping each subsequent entry won't be scrutinized. However, this suggests that the claims that you must always have 500K in your account at all times are overblown. Edited to clarify my post
A lot of people post about their worries about weaknesses in their application. Not sure how likely it is that visa officers lurk on this group, but it might lead to unwanted scrutiny.
It's often taken for granted here that your SP course needs to be at least 6 months long, yet here we have a successful case with a one-month course. And there've been a lot of rejections in Hanoi for SP recently. What seems to have tipped the scale in Op's favor is the 1 mil bht bank balance. In this case, the embassy didn't care if the course was just one month.