Total production increased by 125 per cent to 22,773 barrels of oil equivalent per day (boepd) in the three months to March 31, it told investors today.
That compared to 10,125 boepd in the same period in 2011.
Offshore production reached 21,031 barrels a day with the inclusion of both platforms at Bua Ban North, while onshore, production was 1,742 boepd - an increase from levels seen in the fourth quarter - as natural gas demand recovered after flooding in Thailand late last year.
The onshore figure however was lower than in Q1 last year because of the aftermath of the 2011 flooding as well as the power plant at Nam Phong being shut down for maintenance for around 5 days during the quarter, the firm added.
President and chief executive Randy Bartlett told investors: "The first quarter of 2012 built upon the company's success in 2011."
He also highlighted Coastal's successful exploration discovery at Bua Ban South in the miocene and oligocene reservoirs, where two wells showed successful results.
These discoveries have been appraised and are thought to be commercial.
"We plan to drill further appraisal wells to delineate the discovery once production facilities arrive on location in the third quarter," he said.
"We purchased two production facilities in the first quarter, one at Songkhla A and one for Bua Ban South.
"We plan to continue using a portion of our free cash flow to acquire currently leased production facilities to reduce our operating costs. We are also evaluating bringing in an additional drilling rig to accelerate our exploration and development programme.
"2012 is off to a great start. We all look forward to another successful year with Coastal."
In the first quarter, EBITDAX was US$128.4 million, compared to US$42.5 mln recorded in the first quarter of 2011 - driven higher by the increased production and commodity prices.