International Patent Application
An inventor/applicant can file a patent directly in any country other than India or can apply for PCT (International) patent application within a period of one year from the first filing date/priority date.
The Patent Cooperation Treaty (PCT) is an international patent law treaty, concluded in 1970. It provides a unified procedure for filing patent applications to protect inventions in each of its contracting states. A patent application filed under the PCT is called an international application, or PCT application. By filing one international patent application under the PCT, applicants can simultaneously seek protection for an invention in more than 190 countries.
See PCT contracting states - https://www.wipo.int/pct/en/pct_contracting_states.html
A single filing of a PCT application is made with a Receiving Office (RO) in one language. It then results in a search performed by an International Searching Authority (ISA), accompanied by a written opinion regarding the patentability of the invention, which is the subject of the application. It is optionally followed by a preliminary examination, performed by an International Preliminary Examining Authority (IPEA). Finally, the relevant national or regional authorities administer matters related to the examination of application (if provided by national law) and issuance of patent.
For Official fee, please visit - https://www.wipo.int/export/sites/www/pct/en/fees.pdf
For Calculating a timeline for National Phase filing, please visit - https://www.wipo.int/pct/en/calculator/pct-calculator.html