Thawatchai Jaroennet, also known as Ben, has not contacted his family since he vanished from his house in Leeman, 230km north of Perth, on June 28.
Police say his actions are out of character and hold concerns for his safety.
He is slimly built, has dark skin and is about 190cm tall, with brown eyes and short dark hair. He was last seen wearing blue jeans and a brown jumper and was riding a black 'Giant' brand mountain bike.
Anyone who can help police locate Ben can contact police on 131 444 or Crime Stoppers on 1800 333 000.
Appeal to help find teenager
Updated - ABC
The family of a Perth teenager who has been missing for more than a week has appealed to the public to help find him.
Thayatchai Jarroennet, also known as Ben Jarroennet-Lewis, was last seen walking out of a home in Morcombe Street at Leeman about 10 PM (WST) last Monday night.
The teenager is described as being of Thai background, about 190 centimetres tall with a slim build, brown eyes and short dark hair.
He was wearing blue jeans and a brown jumper and may have had a bicycle with him.
His stepfather Grant Lewis says the family are concerned because they have not heard from him, which is out of character.
"I'm hoping he's just walked off and is safe somewhere, that's what we've got to try and pin down and find out, because there's been no trace of him at all, that's the scariest part, there's just no trace of him, somebody must have seen something."
"It's way out of character for him to just disappear, he would normally contact somebody, he hasn't got any money, he hasn't got a phone, I feel something may have happened."
Police praise helicopter help in search
Posted - ABC
Senior police in the mid west have praised the assistance of the police helicopter in searching for a missing teenager at the weekend.
The aircraft, normally only used in metropolitan areas, was being used during daylight hours to help search for Leeman teenager Ben Jarronennet-Lewis, who has been missing for nearly two weeks.
On Friday and Saturday evening, the helicopter was also dispatched to Geraldton and assisted officers on the ground track and arrest a number of people.
Inspector Garry Cunningham says the helicopter's infra-red cameras could track heat sources such as vehicles and human bodies, and were a valuable tool.
"That normal back up is really only used in the metropolitan area so it was great to have it up here, very positive and I think it's great to see some of the latest technology and tools able to come out to Regional WA," he said.
Stepfather's plea to find teenager
The stepfather of a teenager missing from Leeman has made an emotional plea for help to find the 17-year-old.
Thayatchai Jarroennet, also known as Ben Jarroennet-Lewis, was last seen walking out of a Morcombe Street home about 10pm on June 28.
His stepfather Grant Lewis today said Thayatchai took six packets of two minute noodles, a bottle of water and said he was going for a walk, but has not been seen or heard from since.
"He's a good kid, always has been," Mr Lewis said. "He has always been very helpful, particularly for the elderly."
Mr Lewis said the weeks since Thayatchai's disappearance had been "extremely worrying".
He said Thayatchai may have taken a bicycle with him, and that his recent use of cannabis had caused the family concerns.
"That's why we're getting so desperate to find him," Mr Lewis said.
Mr Lewis said Thayatchai had friends in Jurien Bay, Cervantes and Perth, and was planning to go to TAFE to study engineering, but he missed his enrolment date last week.
"We're appealing for anyone who may have been travelling through that area late at night and seen a kid walking or on a pushbike that might have been out of the ordinary, even to the point of the Brand Highway, to come forward," he said.
"He left school at the end of last year, he had done a little bit of work on the crayboats…he was going to come down to start TAFE and do an engineering course."
Thayatchai is described as being of Thai background, about 190cm tall with a slim build and short dark hair. He was last seen wearing a blue Quicksilver jumper and blue jeans.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000.