Energy Minister Narongchai Akrasanee expects an additional 2,800 megawatts of solar power will enter the national grid by the end of next year.
For 2014, Thailand's solar power is estimated at 1,000 MW.
Mr Narongchai's projection rests on a deadline set by the Energy Ministry requiring solar power licences granted in 2010 to commence operation by the end of 2015 or face revocation.
The ministry expects 2,800 MW out of a total 3,000 MW delayed since 2010 will meet the deadline, while the other 200 MW will have to give up their licences.
After 2015, the ministry hopes to see an additional 1,700 to 2,200 MW of solar power come online over the next 10 years.
By 2020, solar power will approach 5,000 MW and represent 10% of total capacity, up from 0.3% now.
The ministry targets renewable energy making up 25% of electricity output by 2020.
"We have not changed our renewable energy target despite the declining global oil price, as renewable energy is higher cost anyway," Mr Narongchai said.
Mainstream renewable energy includes biomass, biogas, waste-to-power and solar rooftops.
Prof Dusit Kruangam, chairman of the Thai Photovoltaic Industries Association, said his group would propose a liberalisation of the solar rooftop business.
The move is aimed at creating a free market for individual households and businesses to invest in equipment to generate power by themselves instead of waiting for state utility support.
Surplus power from rooftops could be sold back to the power grid.
"This would benefit everyone, as the Electricity Generating Authority of Thailand, the state utility, could cut peak-hour generation and new development of power plants, whilw households and businesses could cut their power bills," Prof Dusit said.
He said the law barring people from freely installing solar rooftops should be revised.
Solar modules are defined as "machinery" and thus prohibited in residential zones under law.
"This definition is the very first that needs amending since it is not practical at all," Prof Dusit said.