Updated 20-Sep-2023
There is a plethora of keyboards available in Android (as opposed to the iPhone), and some have the innovative swiping feature of dragging fingers across the keys instead of individual typing of each key. That is great, and the original Swype is available for free in Beta. However, if there is a need for multilingual keyboarding, that is switching between different keyboards, then Swype is of no use. However, there are two other options:
Swiftkey
Swiftkey is in many ways even more impressive than Swype. For one, it is multilingual (though missing Khmer and Thai). Secondly, it can learn in a much more comprehensive way from your own writing. Thirdly, it knows phrases, not just words. Swiftkey in the Android store.
TouchPal
TouchPal is not as good as Swiftkey, but has multilingual support of Thai. Swiping in Thai is not supported, though. Nevertheless it has a useful keyboard. CooTek the authors of Touchpal have also created a great dialer, the TouchPal Dialer.
MultiLing
MultiLing does not have swiping. However, they do have Khmer. I don't know Khmer, but I do see it in my future, and it is exciting to see a language (and country) that is largely ignored, get to a point when a bit of hacking can make it available on a smartphone. MultiLing is actually hugely comprehensive and may even have Lao script support in the near future. To get Khmer working, though, the Android phone will need to be rooted and then fonts installed. See the Cambodia Android User Group facebook page for instructions and links. Once that is done, install: * MultiLing * English * Khmer * Thai * HanWriting This provides ability to switch between English, Khmer and Thai with a sideswipe on the spacebar. Note also that the Lao language is supported but not with a plugin. Just install the HanWriting plugin and enable it and the Lao language. May need to reboot in order for the phone to display the script properly.
T-Swipe Pro
Update 23-12-11: just tried a new keyboard which has swiping support for Thai and English (and a few other languages) and great customization support for tablets T-Swipe Pro offers a staggaring set of customization options and some great tablet configurations and has both Thai and English swiping and word recognition. Give it a try. It will likely replace my use of TouchPal
Update 08 May 2014
I am traveling to Vietnam in a few weeks, and looked through the keyboards again. SwiftKey now supports both Thai and Vietnamese. TouchPal now has TouchPal X and still is the most complete language support for most European and Asian languages. T-Swipe Pro which is my favorite, doesn't support Vietnamese, unfortunately. My choice for this trip will be SwiftKey because it has a better interface than TouchPal X.
Update 11 Mar 2018
Looks like T-Swipe Pro is still lagging in the languages. Also, SwiftKey has a non-disable-able emoji button that is very intrusive. Like others, I find this a dealbreaker. Finally, Google has a G-Board, which is highly configurable, and includes gesture. Google finally ate the competition, as was expected. It just took about 6 years to do so.