What should I know about border bounces with a METV in Thailand, particularly for Mexican passport holders?

Hi there - METV question. I have a valid METV (Mexican PP holder) and will need to do one more border bounce (for a 60 day entry) before it expires, my holidays ends, and i return home. I have already done 2 border bounces to the Thai Laos border at Mukdahan, since entering Thailand in late April.

This time (yesterday) i was grilled by immigration at the Mukdahan crossing, about what i'm doing, was asked for money, flights, bookings etc. Which was a bit unexpected as i thought they we're fairly relaxed.

Three questions: 1) are there many reports of Land crossings getting more hard-core? 2) as a mexican can i do a border bounce to the Mae Sai border? (Plan to travel to Chiang Rai anyway), and 3) Will i be asked for a TM30 to get a 30 day extension on an METV entry? Previously Tod said this wasnt required, but i think this may have changed. Thank you very much!