Learn English – Dessert, countable vs uncountable

In this case field is the head of its noun phrase, and adding paddy as a modifier to field does not change its status.

In some areas, some paddy fields could be found among the river, houses, etc.

Note, however, that in English paddy may be used for either the crop (rice) or the field, and in ordinary non-technical use usually means the field; we tend to speak of (rice) paddies rather than paddy fields, and paddy fields will sound odd to non-specialists.

The sentence has two other problems.

• The second some should be replaced. Some has two fairly distinct meanings: "neither all nor no" and "an indefinite number". Since your sentence appears to start by using some in the first sense "In some (but not all) areas", it is jarring to use it again so quickly in the other sense. Say a few or occasional or frequent, if appropriate, or if you want to leave it as indefinite as possible simply leave the determiner off: "Paddy fields could be found ..."

• It is very jarring to cast a non-collective singular like the river as an object of the preposition among. Among may take a singular collective (the crowd) as an object, but a conjoint object (A, B and C) is not taken as a whole: each of the conjoined entities should be a plural, capable of acting by itself as the object of among. Use a different preposition here: perhaps alongside.

Sugar is uncountable: grains of sugar are countable.

Air is uncountable: oxygen molecules are countable.

Money is uncountable: dollars are countable.

Sometimes we want to use a collective term for stuff that you use to buy things with- that's money. When you want to start quantifying (counting) it, you have to use a currency- dollars, dinars, yen, euros.