I would bet on Czech, India to build a Thorium reactor first.
Japan, Norway could also get involved early.
Canada or France could help make one for someone else (probably India)
WNA News Briefing, India: Construction of the country's first advanced heavy water reactor (AHWR), using a thorium fuel cycle, will reportedly start during 2007.
India is developing the Advanced Heavy Water reactor (AHWR) as the third stage in its plan to utilise thorium to fuel its overall nuclear power program. The AHWR is a 300 MWe reactor moderated by heavy water at low pressure. The calandria has 500 vertical pressure tubes and the coolant is boiling light water circulated by convection. Each fuel assembly has 30 Th-U-233 oxide pins and 24 Pu-Th oxide pins around a central rod with burnable absorber. Burn-up of 24 GWd/t is envisaged. It is designed to be self-sustaining in relation to U-233 bred from Th-232 and have a low Pu inventory and consumption, with slightly negative void coefficient of reactivity.
The India - US nuclear deal is in trouble
UPDATE: India has shelved the US-India nuclear deal. Parts of the ruling coalition do not want to give up sovereignty and allow inspections of India's nuclear sites
India on Tuesday approved purchase of equipment for implementation of two 700 MW pressurised heavy water reactors each in Rajasthan and Gujarat.
Some of the other advanced reactors in development could also use thorium
High Temperature Reactors (HTRs) can potentially use thorium-based fuels, such as HEU with Th, U-233 with Th, and Pu with Th. Most of the experience with thorium fuels has been in HTRs.
A larger US design, the Gas Turbine - Modular Helium Reactor (GT-MHR), will be built as modules of 285 MWe each directly driving a gas turbine at 48% thermal efficiency.
South Africa's Pebble Bed Modular Reactor (PBMR) is being developed by a consortium led by the utility Eskom, and drawing on German expertise.
The Czechs working on molten salt reactor
Canada's Candu reactors can burn thorium and with modifications could burn it far more efficiently
A recent Canadian design for a modified geometry 2 fluid Molten Salt Reactor
The French have a lot of active research into Molten Salt Reactors
Japan researchers published peer reviewed plan for shifting to thorium fuel cycle
Thorium fuel mix in past Indian nuclear reactors
another overview of Thorium reactors