get yourself a job and work permits in Thailand, otherwise fairly impossible at all, giving the timeframe.
and what do you mean that you will work in Shanghai / Singapore..? remotely from Thailand..? as you will not be able to shuttle between TH and other countries.
when someone had been caught with irregularities then they are left with their problem, from time to time there are reports on this, for last couple of years these reports piles up into some number.
it's nothing Thailand specific, all the SEA area has a similar problem when visa agents push the limits, just for different points and needs.
among other things agents from time to time stretch legal limits and agree with Immigration on smth. what Immigration should not have done - when it's come to the light, it's often a problem for the customer. If this result that a customer used smth fake or at the moment of review is happening actually to be on overstay (wrongly assuming he's not) then it dealt in a due course of justice, like IDC etc., there is no mercy shown for that.
what I was saying that bona fide customers of visa agents in case of irregularity on the side of visa agent, getting no excuse or indulgence
of course irregularities are on the shoulders of customers , where else the irregularities can be - depending on a kind and degree of an irregularity an appropriate punitive and or remedial action is taken.