Self employed in the UK and a non-EEA country
If you are self-employed in the UK and a non-EEA country and you are ordinarily resident in the UK, you will have to pay Class 2 contributions (and in certain situations, Class 4 contributions) to the UK scheme. You will not have to pay contributions to the other country's scheme. To make sure that you are not asked to pay, ask the HMRC Residency for a certificate or letter confirming your UK NI liability.
If you are self-employed in the UK and a non-EEA country, but you are ordinarily resident in that non-EEA country, you will have to pay social security contributions to that country's scheme. You will not have to pay contributions to the UK scheme. To make sure that you are not asked to pay, ask the authorities of the country you are ordinarily resident in for a letter or certificate confirming that you have to pay into their scheme. See Addresses for enquiries about contributions and benefits.
