The polls on Sunday will be observed by foreign delegates and members of international organisations, although the European Union says it is not fielding an Election Observation Mission (EOM) as it was not given enough time to prepare.
Election commissioner Loetwirot Kowatthana said on Saturday representatives from 11 countries and International IDEA, a democracy advocacy group, attended a forum to familiarise themselves with the election before they began their observations.
Sunday's polls will also be open for longer than in previous elections; polling stations will be open between 8am and 5pm, while in the past they closed at 3pm. Voter turnout is expected to exceed 80%.
Many polling stations are expected to be busy today after the advance voting saw 82% of registered voters casting their ballots last week.
It was reported that the foreign observers will be split into two groups: one invited by the Election Commission (EC) and another which requested observation access from the EC.
The invited group is made up of 42 foreign observers who are election officials from Asean countries. They will be watching the poll procedures and the EC's roles in Bangkok and neighbouring provinces until Tuesday, Mr Loetwirot said.
The second group, which requested access through their respective embassies, includes Australia, Canada and the United States, as well as European-based poll-related international organisations and the Asian Network for Free Elections. This group consists of 145 observers.
Meanwhile, the EU said election observation requires the long-term, country-wide presence of an independent EOM in accordance with the Declaration of Principles for International Election Observation.
This requires an official invitation from the host country and four to six months of notice to prepare for the mission, including the deployment of long-term observers. In the case of the Thai general election, the EU did not receive such an invitation within the required timeframe.
In the absence of an EOM, the EU Delegation -- alongside diplomatic missions from some EU Member States -- has registered a number of its diplomatic staff members accredited in Thailand for participation in what is commonly referred to as a "diplomatic watch".
This entails visits of accredited persons to polling stations on election day to develop a general sense of the conduct, to be used primarily for internal reporting. Such activities are small both in numbers and geographic scope and therefore do not constitute an "election observation". They are not sufficient for formulating an overall assessment of the electoral process and cannot form the basis of any public statement.
But an EU statement said it "welcomes the holding of elections as a milestone on the country's path back to democracy and wishes all Thai people a peaceful and meaningful election day".
United States representatives have also reportedly arrived in constituencies in Nakhon Si Thammarat and Si Sa Ket to observe the election in an unofficial capacity.