Yes, a Partner visa applicant can use income from employment in a foreign country, if the following conditions are satisfied:
The application is filed outside the UK, i.e. an Entry Clearance application is made
The Applicant and the Sponsor (plus any Dependant children - aged under 18) are living outside the UK and the whole family wishes to come and live in the UK
The Sponsor is in employment outside the UK, earning a Salary in foreign currency equivalent at least GBP 18600 (or higher - if applying with dependants, see forum answer on "How much income is required to meet the financial requirement"),
The Sponsor has secured a job in the UK and has a signed contract with his prospective UK employer with at least a Salary of GBP 18600 (or higher - if applying with dependants) and the starting date of the employment is within 3 months of the Sponsor's return to the UK
Any shortfall can be met with Cash Savings (see forum answer on "How to meet the financial requirement with Cash Savings?")
NB: The Applicant's employment income, either foreign or future UK income, cannot be used to meet the Financial requirement in this case.
[the foregin currency conversion should be applied as per the currency converter on the website https://www.oanda.com/ on the date of application. The date of application is the date on which the online application is submitted and the Immigration Health Surcharge and UKVI fees are paid]