However, registration was trouble-free in Bangkok and the rest of the country, following violent clashes that had impeded political party registrations in the capital earlier in the week.
Candidates registering included Wan Yubamrung, son of the combative caretaker labour minister Chalerm Yubamrung; four members of the family of veteran northeastern political warhorse Sanoh Thienthong; Chartthaipattana leader Banharn Silpa-archa and his son; as well as relatives of some other prominent politicians.
The six affected provinces are Krabi, Nakhon Si Thammarat, Songkhla, Chumphon, Trang and Phuket, said EC secretary-general Puchong Nutrawong.
Although the EC had not ordered a halt to registrations in Surat Thani, poll officials and candidates were still not able to enter the registration venue, to which water and power supplies had been cut.
The EC would wait until 4.30pm to decide whether to stop, he said.
In Nakhon Si Thammarat, election officials were not able to enter a building they had planned to use for candidate registration work after the owner, who was intimidated, refused to let them use it.
Protesters at the site used loudspeakers to criticise the government and the EC for not calling off the Feb 2 poll.
In Chumphon, the venue was surrounded by more than 100 anti-election protesters who also cut water and electricity supplies. Candidates were not able to get inside, but no violence was reported.
In Surat Thani, protesters laid siege to the registration venue and no candidates turned up to register.
In Krabi, another group of protesters led by the People's Democratic Reform Committee (PDRC) put up a large "Reform first, then election" sign in front of the election centre.
No violence was reported, but only two candidates and one official managed to slip into the registration venue.
In Songkhla, the registration site was blockaded and no candidates had turned up.
Nakhon Si Thammarat, Chumphon, Surat Thani, Krabi and Songkhla have a total of 29 constituencies.
It was reported that members of the Songkhla election committee had announced their intention to resign today after encountering problems.
Somchai Srisuthiyakorn, the commissioner in charge of election administration, said the EC had advised provincial election chiefs to try to negotiate with the protesters or move to new venues.
Candidate registrations have to be carried out from Saturday through Wednesday and the dates cannot be postponed, he added.
Mr Puchong said the situation was normal and candidate registration was going ahead in 16 northern provinces.
Registrations also were trouble-free in the 20 provinces in the Northeast as well as in all of the Central and eastern provinces, officials said.
The North and Northeast are the strongholds of the governing Pheu Thai party while the Democrats, who are boycotting the Feb 2 poll, dominate the South.