Automatic Top-Up for dtac?

How do you guys deal with top-ups for prepaid dtac?

I know for postpaid, one can set up automatic debit, but for prepaid it seems the best option is to set up a weekly or monthly top-up via your bank’s app, this is a bit annoying though, as you can only select preset amounts, e.g. 400 baht, and I have a dtac package which is not a round number (few of them are), nor is it paid “monthly” but instead every 30th day.

I generally want to keep a zero balance because if I don’t have a package, background internet activity on my phone will quickly use up whatever balance I have, likewise, I have dual SIMs, and it happens that I accidentally answer incoming Thai phone calls while outside Thailand, which will also burn through my balance.