1

They have similar in Belize (i.e.Placencia) but not for $20. In Costa Rica you are not aloud to build on the beach (the "maritime zone") except for certain exclusions which prevents these type of buildings. They used to have them in Playa Coco which Ticos used as very cheap lodgings at weekends but I'm pretty sure they've knocked them all down now. Some of the lesser known beach towns on the Brazilian coast have them....

2

Yes these are called Cabinas, and they are more on the caribe coast of Central America, then the Pacific coast. But for $20, that will be a challenge, things are tad more expensive on the beach in Central America. Double/Triple that. Another issue is the beach, its is hard to find a combo of nice sand and calm waters with no sand fleas.

On Roatan Bay Islands Honduras, this place has old school cabins, but its on a rock reef, no beach/sand.

http://www.seagraperoatan.com/ Great if you scuba...

Or Dereks Place on the Corn Islands in Nicaragua.

http://www.dereksplacelittlecorn.com/en/cabanas/index.php

Or on Pt Viejo area of Costa Rica...

http://www.cabinaspuntauva.com/images_esp.html

and there are some very cool and nice places on the islands in Bocas Del Toro Panama...

http://redfrogbungalows.com/bungalows

I would love to check out this place in Belize on Glovers Atoll.

http://www.glovers.com.bz/

Overall the beaches and topography are much different in Central America, add to this the cultural lifestyle, and you just cant replicate Thailand's great beaches, calm waters and pleasant climate.

Costa Rica Pt Viejo area is most popular for this rustic lodging, but directly on the beach, across the road is the norm.

http://www.puertoviejosatellite.com/stay.php

There are more boutique bungelows on the Pacific side, some perched above the ocean for a nice breeze, usually near surf beaches, can be $$$.
http://www.milarepahotel.com/bungalows.html

3

Tulum, Mexico! It's all about cabañas ( that's what bungalow are called in Spanish). You won't find anything for 20$ though ( unless you want to camp. You can do that right on the beach in Tulum).
40-50$, really basic cabañas with shared bathrooms. More decent ones 90-100, and up a night.