Triple World Superbike champion Jonathan Rea took his first win of the 2018 season with victory in race one at Buriram in Thailand on Saturday.
The Northern Irishman pulled away to win by 1.5 seconds from Spaniard Xavi Fores, with Welshman Chaz Davies third.
Rea trails Marco Melandri, a double winner at the opening round at Phillip Island, by two points at the top of the standings ahead of Sunday's race two.
Rea now has 55 World Superbike wins, four short of Carl Fogarty's record.
The Kawasaki rider is aiming to equal Fogarty's record of four titles - although the Englishman's series successes did not all come in consecutive seasons.
The 31-year-old has won six of the seven races in the championship held at the Chang International circuit in Thailand, including doubles in 2015 and 2017.
The defending champion finished fifth and second in the first round of the series at Phillip Island as he struggled with the effects of illness and overcoming surgery on a hand injury following a motocross training crash.
Rea secured pole position for the 20-lap race in Thailand and was involved in a three-way battle at the front with team-mate Tom Sykes and Honda-mounted Leon Camier in the early stages before hitting the front.
"I don't have that relationship with my bike that I had last year, when I felt I could do anything with it that I liked," said Rea after his triumph.
"This year is really hard work but the team are working so hard to give me the best bike that they can.
"That was a tough race and Xavi really kept me honest but it was important that I go out and stamp my authority on proceedings."
Camier finished fourth, with fellow Englishmen Alex Lowes and Sykes completing the top six.
Italian Melandri, who started from seventh on the grid after a crash in Superpole, could only manage an eighth-place finish, while Eugene Laverty was ninth on the Milwaukee Aprilia.
|2018 WSB Riders' Championship|
|Marco Melandri (Ita)||Ducati||58 pts|
|Jonathan Rea (Gbr)||Kawasaki||56|
|Xavi Fores (Sp)||Ducati||49|
|Tom Sykes (Kaw)||Kawasaki||43|
|Chaz Davies (Gbr)||Ducati||32|
|Leon Camier (Gbr)||Honda||32|