It's expected that even nations that have declined to show recognition for the military takeover of the country on May 22 will make an exception for the commemoration of the big wave.
Envoys from many countries are expected at the Khao Lak ceremony.
Just under 5400 tourists, expats, Thais and Burmese workers were killed in 2004 - although an error made for the first anniversary means a figure of more than 8000 deaths is sometimes quoted.
This is because authorities failed to take account of the work of the Thai Tsunami Victim Identification unit and remove names from the list of missing as close to 3000 nameless bodies were identified.
The tsunami represents the worst natural disaster for Thailand, and also for Sweden. A total of 543 Swedes were killed.
Almost as many Germans died, too. About 800 people were killed in the village of Nam Khem (salt water) in Phuket's neighboring province of Phang Nga and a similar number perished on the island of Phi Phi in Krabi.
Although Phuket at the time had 10 times the population of Khao Lak, 10 times as many people were killed in and around Khao Lak as on Phuket. The toll on Phuket was about 330.
While the west coast was badly battered, access to the disaster zone enabled thousands of volunteers to quickly recover the bodies and begin reconstruction.
The key ceremony on December 26 will take place in the evening at the patrol boat that was washed more than a kilometre inland. It will be telecast live in Thailand and Sweden.
People from more than 40 countries lost their lives in Thailand and most of them are expected to be represented in Khao Lak.
The world heard first about what had happened when the tsunami struck the Andaman coast, and the outpouring of generosity became much greater when the nightmarish total toll of more than 220,000 was calculated in Indonesia, Sri Lanka, India and other affected countries.
At least one smaller ceremony is planned for Patong beach on the evening of December 26. Candles are usually placed along the sand.