A teenager who discovered he had an aggressive brain tumour after having a seizure in his sleep has travelled to Thailand for treatment.

A CT scan last April revealed Greg Lewis, from Bunbury in Western Australia, had calcification on the brain — most likely due to a vein bursting when he was a child.

“I had no symptoms of a brain tumour before I was diagnosed when I had the seizure in my sleep while I was staying at my friend’s brother’s house,” Mr Lewis told Yahoo7 News.

“I was rushed to the hospital a few days later.”

An MRI confirmed the then 18-year-old had a 30 millimetre brain tumour and he was started on a six-week course of chemotherapy and radiation.

But the treatments were unsuccessful and the tumour has increased in size.

“I’ve under gone two brain surgeries – the first was in June then the second was on the 23rd of November – the day after my 19th birthday,” Mr Lewis said.

Mr Lewis’ family said he had limited options and decided to travel to a cancer clinic in Thailand.

They have set up a GoFundMe page hoping to assist with expenses.

“The treatment in Thailand is envisaged to be 8 weeks in duration, and as such will be very expensive,” a post the GoFundMe page said.

The teenager and his mother set off for Thailand on Sunday.

“I went through 33 sessions of radiation and three rounds of chemotherapy with no success,” Mr Lewis said.

“This clinic uses modern medicine and natural methods to combat cancer.”