Rea battled with Kawasaki team-mate Tom Sykes throughout Saturday's 20-lap race and two-tenths of a second separated the pair at the chequered flag.
The second race at the Buriram circuit will take place on Sunday.
Reigning champion Rea won the first two races of this year's championship at Phillip Island a fortnight ago.
The 29-year-old has accumulated a perfect total of 75 points and already enjoys a 23-point lead over nearest challenger Michael van der Mark (52), with Sykes third on 41 and Davies fourth on 39.
Pole position man Van der Mark took the final podium spot on his Honda, with Welshman Chaz Davies fending off the challenge of fellow Ducati rider Davide Giugliano to take fourth.
Sykes took the lead early in the race following an uncharacteristic error from Rea but the Northern Irishman regained his position at the front with four laps left, going under the Yorkshireman on the brakes into the last corner.
Former world champion Sykes made a last-ditch attempt to edge in front in the closing stages but was unable to get past the Isle of Man-based pacesetter, who set the fastest lap of the race at 1:33.936 on lap 14.
Jonathan Rea continued his winning start to the season by taking victory in the opening World Superbike race at the Thailand round of the series.