A Perth couple staying in Phuket say they have been in lockdown at their hotel for more than five hours due to a suspicious package outside, as Thailand is rocked by a string of deadly co-ordinated attacks.

A series of bombings over 24 hours have killed at least three people and injured dozens more, some of them foreign tourists. Two of the bombs exploded in the popular Thai tourist town of Hua Hin.

Simon and Nicole Brown from Rockingham said police have cordoned off a 200m perimeter outside their Patong Beach hotel while they inspect the package.

Mr Brown said the hotel has been in lockdown since 8.30am (local time), half an hour after a device went off on Bangla Road.

The couple arrived in Thailand on Wednesday night and felt an unprecedented atmosphere of unease.

One of the Hua Hin bombs was hidden in a pot plant. Photo: Getty

“It was the first time in 10 to 15 years of coming here that we mentioned to ourselves that things felt different,” Mr Brown said.

“There’s a little bit of unease in the air, we just put it down to the recent referendum and the Queen’s birthday.”

He said that staff have handled the situation very well, yet there was a sense of tension.

“If things escalate we’ll be on the next flight home,” he said.

Australians have been warned to exercise a “heightened caution” in the country and follow the advice of local authorities.

‘There was a lot of blood’

One bomb of the bombs in Hua Hin was hidden in a pot plant.

It exploded on a road outside a bar, followed by a second blast just 50 metres away around 20 minutes later.

A Thai woman selling papaya salad at a street cart was killed in the second blast, police in the seaside town confirmed.

Local police said officials were still investigating a motive and the type of explosives used.

A witness described seeing blood everywhere. Photo: Getty

Hua Hin’s major hospitals told the ABC 11 foreigners are among the wounded.

Three were Dutch, seven were German, Austrian or Italian, and one person’s nationality remains unknown, the hospitals said.

No Australians are believed to have been hurt in the bombings, which happened ahead of a public holiday to mark the birthday of Queen Sirikit.

The blasts also come days before the one-year anniversary of the last major bombing in Thailand, an attack outside a Hindu shrine in Bangkok that killed 20 people on August 17, mostly foreign tourists.

Wildlife Friends Foundation founder Edwin Weik told the ABC he was at the scene around 10 minutes after the blast.

“There was a lot of blood, towels, tissues, I mean all kinds of stuff that people use to stop the bleeding of the wounded people,” he said from Hua Hin.

“I saw that on two different sides, about 100 metres away from each other … where tourists are going to have drinks and walk around, two bombs went off that were planted in pot plants.