I'm unaware of any evacuations taking place anywhere in the Indian Ocean. There's no tsunami warning infrastructure or network. These tsunamis hit probably 1-3 hours after the quake in most places. Places like Sri Lanka probably felt very limited shaking due to distance from the epicenter. Only warning you get is the water going out before it comes in.
I'm just surprised that Thailand never developed such a system, specifically for the island of Phuket. I know that the universities in Bangkok do some inter-college seismic research, but I guess that never included sophisticated monitoring equipment in their own region. Or if it did, the communications capability was not robust enough to get the message to the people who needed it.
When we look back on this calamity, the lesson to take away is something as simple as a warning siren on the key beaches of India and Sri Lanka could have saved thousands. Though a lot of Indian fishermen look dirt-poor, in a group of them, one man will often have a cellphone. If there is a basic warning system in place, people will be able to take care of themselves.