Is it difficult to find a parking lot at the government complex, chaengwattana? Taxi a better option? 

I've never had a problem parking in the roadside spaces right opposite the entrance to immigration.

 

I'm usually there about 7.30AM (we have queue wallah to get a number).

I always park in the multi story opposite end from immigration on the 3rd floor. The guards there say no places are reserved despite what the signs say. Never had an issue. But as above says the earlier you are there the more choice you have.

Always find space opposite the entrance on the street. Multilevel parking is restricted to employees I have been told.

I have done it many times.  Park in building B (blue code).  The entire carpark is always packed, but I've found the best location to be level 2 near the area that is officially reserved for Centra hotel.  Level 2 is the same level as walking bridge to Government Complex B.  If no spaces in the Centra slots, I have usually been able to find a spot double parking nearby (leave car in neutral). 

 

I've made 6-8 trips there in the past couple of months and always found a spot in this level 2 area. In previous visits I had trolled around levels 3-4 and it was always very difficult to get a spot (I think visitor parking is supposed to be level 2, but markings are non-existent, so try the hotel area first).  I have personally never parked on the street after a dozen or more trips there in past few years, but I suppose that's an option too.

I always park right HERE. No need to cruise around parking garage for ages. If no spaces then park along the road and leave car in neutral gear with brakes off (you'll see other cars doing same). Then just walk up the ramp and into the building.

Got there today at 8.20, plenty of parking spaces just opposite the entrance. And it wasn't full when we left at about 14.00.