You can get one the same day, although it costs a little more for the ecpress service.
The visa office opens I think 8.30-9.30 in the morning you have to go and fill in the form along with two passport size photos and get them into the office during these hours, then you return in the afternoon pay your money and get your passport back with the visa inside.
2007-04-24 The consular section of the Chinese Embassy will not open to the Public from May 1-7 for Chinese holiday.The consular section will open again on May 8.
You need to check for chinese/ thai holidays etc, the above one relates to last year so would presume one this year at a similar time.
Chinese embassy is right on the corner of ratchada and soi three, visa processing is in an office building on the left as you turn into soi 3.
