Just as an antidote to all the problems!!:

We had three encounters with Thai Bureaucracy yesterday March 10

Required:

Renewal of Thai Passport for Child

Re-Entry Permit

Extension of Stay beyond 90 days

Renewal of passport formalities completed in 35 minutes..would have been less if child wrote name smaller..oh cost 1035 B including EMS delivery..cost of UK Passport approaching 5000B

Re Entry Permit from submission of papers to receipt 8 minutes,,Can you get such a thing in the UK? Cost 1000B

Extension of Stay..including 3 interviews with various pooh-baas 40 minutes Again no such thing in UK .cost 1900B..Cost of UK visa 3500 or ??I think approaching 30000 Baht if you want your wife/partner to have right to remain!!

Chiang Mai the place to be...and the passport office has an ATM, a Post Office and, strangely, a room with a large number of unpacked wheel chairs. While immigration has a pleasant coffee shop....and in Soi Suan Plu and Laksi?? Let alone in Croydon or Central London...and it took 7 hours including a lock out of wife and child (not enough chairs) to get my wife a French Schengen Visa in South Kensington....etc

I've had varying experiences with Suan Phlu immigration from good to appalling for extening my wifes non-immigrant visa.

But as you say, the Thai passport office is a model of efficiency that would put most operators - public and private - to shame, anywhere in the world.