Yes, I have done this.

However, it is somewhat problematic knowing which gate the aircraft is arriving at. THAI staff were able to assist me, but I have suffcient language thai skills to help me out and also held a special access pass - so security interested in questioning me. Probably, this is frowned upon ...

Noting this, I think a rendevous on the departures level, once you both have your boarding passes is lower risk - and made easier if you both have roaming mobile phones so you can be assured your companion has arrived safely.

You could meet at a coffe shop (Black Canyon or whatever), located the intersection of A/B/C/D or D/E/F/G (ie at the floor above respective transfer desk areas).

Cheers, TK