Police said on Monday that one bomb exploded around 7am near Sun-ngai Padi police station in Narathiwat province, killing a rubbish collector and wounding his two colleagues and a police officer.
Police said they were investigating where the bomb was planted - inside the waste-disposal truck or near the police station's entrance - its type and how it was detonated.
Many of the nearly daily bombings in the southern provinces have been triggered by mobile phones, leading the authorities to register sales of pre-paid mobile phone services.
Another bomb exploded around 6.45am at a commercial bank in Narathiwat's Waeng district.
No one was injured, but the bomb damaged the bank's front doors. Police do not know exactly where the bomb was planted or whether any money was stolen.
Police inspect damage in front of
the Sungai Padi police station
At least 700 people have died since January 2004, when an insurgency began that police say is a volatile mix of Islamic separatist unrest as well as organised crime and smuggling.
The killings originally targeted security forces and government officials but have spread to teachers and other civil servants, Buddhist monks, and Buddhist and Muslim civilians such as farmers and shop owners.
Meanwhile, in nearby Pattani province, Buddhist twin brothers were shot with an M-16 while riding their motorcycle home from school, police said.
One boy was killed instantly and the other was wounded.
The government has imposed martial law in parts of the three southernmost provinces to curb the violence, which first erupted in January 2004 when gunmen raided army barracks and stole 400 assault rifles, including M-16s.
Shootings, bombings and arson attacks have since become daily occurrences.
However, authorities in the mainly Muslim region, which has a century-long history of often violent opposition to the Buddhist government in Bangkok, appear no closer to bringing an end to the unrest or identifying its masterminds.