We have half a dozen of DSL-604T in service. it seems to be very popular modem/router in Thailand. unfortunately, it doesn't perform well if it is not configured correctly.

Most of routers we seen, come with Australian version of firmware, which is not bad, but D-link people created special version for Thailand only.

There is not much of a difference between firmware kernels build for different countries, except default settings, but we found that flashing router with a proper firmware helps to overcome problems such as dropping ADSL connection and inability to dial up automatically. This prevents router from establishing connection to upstream router when ADSL connection is dropped. Many people found the only way to re-connect is to disconnect router power supply for 10-15 seconds and then reconnect.

Thai firmware could be found at D-link site in Singapore:

http://www.dlink.com.sg/support/support_detail.asp

For safety, we recommend to flash your DSL-604T router using web interface. Latest firmware is V2.00B01T01.TH.20061120, as you can see, it has TH properties and much better on TOT network than older V1.04

Just to remind you that TOT in Pattaya use VPI=1, VCI=32, G.dmt modulation and ANNEX_A. Most routers will have an option to set modulation and annex mode to automatic. We found that forcing it to G.dmt and Annex A produce better results.