Normally, you would require a residence permit for being able to work in Finland.
For seasonal work, however, you do not require a work permit. You will need a visa for taking up seasonal work in Finland.
By seasonal work is meant agricultural and tourism-related work done at only certain times in any year. For example, picking of wild berries.
The visa is intended solely for seasonal work in Finland. You may be issued a visa for up to 90 days.
For the processing of seasonal visas, the regular processing times set out in the Visa Code are valid. A seasonal work permit is issued to one or more designated employers and a seasonal worker does not change his or her employer during the seasonal work period.
You will need a short-term visa to visit Finland which is valid for 90 days. This short-term visa is also known as the Schengen visa. As you may be aware the Schengen visa is valid in all the European countries which are part of the Schengen agreement. Finland is one of the countries under the Schengen agreement.
With a Schengen visa you can travel to and stay in Finland and all the other 26 Schengen countries.