Two bombs have injured at least 18 people in southern Thailand, just hours after another blast killed two people in a neighbouring province.
Thai PM Thaksin has been criticised by Muslims in the region
The attacks come amid rising tensions over the deaths in army custody of 78 Muslim protesters earlier this week.
Malaysia's former Prime Minister Mahathir Mohamad has urged Bangkok to consider giving autonomy to southern Thailand's Muslim Malay majority.
He told a local paper that early action could prevent a violent escalation.
The first of Friday's bomb blasts exploded near a tea shop in Yala province, injuring eight people, including three police.
About 90 minutes later, as police were investigating, another bomb went off. Twelve police were injured in this blast, four of them critically.
25 Oct: Protest in Narathiwat turns bloody - 85 dead
26 Oct: Muslim separatists vow revenge
28 Oct: Bomb attack in Narathiwat - 2 dead
29 Oct: Two blasts in Yala - several injured
Friday's attacks came in the wake of a deadly bomb on Thursday, and a protest on Monday which ended with 85 dead.
Seventy-eight of these died after being suffocated or crushed after over 1,000 people were loaded into army trucks following their arrest.
Seven others died in clashes with security forces outside a police station in Takbai, in Narathiwat province.
More than 400 people have now died in southern Thailand this year in mounting violence blamed on the security forces and Islamic separatist rebels. One separatist group this week vowed to avenge the latest deaths by attacking Bangkok.
Thai Prime Minister Thaksin Shinawatra is due to address the crisis in the south when he makes a televised address later on Friday.
Thursday's bomb hit a bar in Sungai Kolok, on the Malaysian border in the southern province of Narathiwat.
Two people, reportedly a Malaysian tourist and a Thai woman, were killed and 20 injured.
It is not clear if the bar was the intended target - a police station and beauty parlour are also said to be nearby.
A bar in Sungai Kolok was also targeted in a bomb attack in May.
The BBC's correspondent in Malaysia, Jonathan Kent, says border security in this area is very lax and many locals pass through unchecked.
Our correspondent says it underscores Thai claims that separatist guerrillas may be crossing from Malaysia, a charge the Malaysian authorities deny.
Nevertheless, the Malaysian government has expressed concern that the violence could spill over into its territory. Hundreds of Malaysians gathered outside the Thai embassy in Kuala Lumpur on Friday to protest about the killings.
In an interview with a Malaysian newspaper, former Prime Minister Mahathir Mohamad said autonomy for Thailand's southern Muslims - whose ethnic roots are Malay - could help stem the violence.
But he told separatists in the region that they could not expect to win independence.
"The best they can hope for is the formation of an autonomous territory... whether (autonomy) is possible or not is not the point, but it needs to be worked at," he told the Utusan Malaysia newspaper.
A separatist rebel group opposed to Bangkok's rule in southern Thailand, the Pattani United Liberation Organisation (Pulo), has vowed to avenge the latest deaths.
"They will pay for what they have done, their cities will burn," said a statement posted on the group's website.