... I checked full text of this document and there's no information about E31A at all so does it mean with E31A it's allowed to work informal?...
From
https://evisa.imigrasi.go.id/web/visa-selection
Type of Visa E31A - 1 YEAR or 2 YEARS
3. With this visa you can
Carry out employment-related activities or attending education, as long as it has been reported to Immigration (using the multiple activity reporting process).
Travel to and from Indonesia as many times you want.
Conducting activities related to tourism, and visiting friends or family
5. Other information
e. You are prohibited from working by receiving compensation, wages, or any similar from individuals or companies in Indonesia, unless reported to immigration (using the multiple activity reporting process).
Poster's Note : I recommend the interested foreigners to inform Immigration "using the multiple activity reporting process" as mentioned above , regarding any work plan you may have .
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As far as I know , there is no issued information from Immigration or Manpower about "informal work" . The "informal work" subject probably first came from a "PERCA/Indonesian Mixed Marriage Organization" article about a meeting between them and 1 Immigration officer + 1 Manpower officer in March 2015 . It was published at
http://percaindonesia.com , but it is not there anymore (I don't know why) . See below a copy that I saved from that time .
Summary of the meeting (free translation and some words changed for clearness) :
[.....
A) Holders of KITAS/KITAP sponsored by Indonesian spouse are allowed to work in a company ... having a work permit .
B) Foreigner workers cannot work in two different places (the same profession or different) EXCEPT investor director / commissioner of PMA (If one works in three places , 3 work permits are required .
C) If the activities of the foreign worker are in more than 1 place / province then he/she must have inter-provincial work permit .
D) Case: Foreigner of a mixed marriage with cuisine chef background want to open a small café, with a small seating area is classified as a small business and does not require a work permit . When this business grows crowded and large, than it is necessary to have operating permits from the relevant authorities . When the businesses becomes a legal entity, then this foreign worker must have a work permit .
E) Case: Foreign of a mixed marriage is already retired. Enters Indonesia with VOA and becomes an investor in a hotel in Bali. Once in a while he does work behind the scenes such as checks on the financial control department. With such conditions, it means the foreigner has been conducting work in Indonesia and must have KITAS and work permit , because even not all the time he/she is working .
F) A foreigner in a mixed marriage with KITAS sponsored by the Indonesian spouse . Working from home and having online business . Does not have an office and legal business such as PT or PMA . Because this foreigner is conducting work even though he only works online so this foreigner must have a work permit . This foreigner also cannot sign work contracts in Indonesia on behalf of himself/herself .
G) A foreigner who works and own business as an acupuncturist, must obtain an official recommendation from the local health office before doing business and work activities. If already have a recommendation from the relevant authorities, the foreign must have a work permit to be able to work in Indonesia .
H) A foreigner holder of KITAS/KITAP sponsored by spouse is allowed to work in Indonesia. The need of a work permit is to be seen from what the job is , workings for a legal entity or not, small or large business .
CONCLUSION:
Although the Immigration Law no. 6 of 2011 Article 61 states that the holder of a KITAS/KITAP can work and/or do business to make ends meet for him/her and/ for his/her family, the foreigner still has to refer back to the Labour Law no.13 year 2003 and Labour Regulations , which essentially means that a foreign worker in a mixed marriage is allowed to work without a work permit if in the informal sector, freelance or have a small business which is not a legal entity. When working in a legal entity then the foreigner MUST have a work permit.]