Fund and funds are two different words:
- Funds is an indeterminate, uncountable amount of money or currency. (Def.n 2 in OLD.)
- A fund is a countable noun meaning a collection of money to be used as payment or capital towards a certain purpose; account is a rough synonym. It offers no indication of how much money has been collected. The plural of this word is funds. (Def. 1 in OLD; def. 3 has the same meaning, just not necessarily about money.)
I've omitted the use of fund as a verb because it's not related to the question at hand.
A fund contains funds. For example:
Accounting needs to know which of our funds (2, plural) provided the revenue for the purchase.
The petty cash fund (2); it didn't cost very much.
Will we have enough funds (1) remaining in that account to buy lunch for everyone?
If we don't, we will have to wait until after our client's funds transfer (1) has gone through.
I'm surprised to hear that Indian English refers to a general movement of money from one account to another as a fund transfer. British, Australian and American English call it a funds transfer or transfer of funds. This makes more sense semantically, because fund transfer seems to imply a change in ownership of the account rather than a movement of money.
For example (ignore the electronic bit, it's not relevant to our discussion and just makes the term easier to search): Cambridge, Dictionary.com, Australian bank. Additionally, Google Books Ngram Viewer and the Corpus of Global Web-Based English both indicate that funds transfer is more popular by a wide margin. GloWbE shows that India prefers funds 67 to 37, though Bangladesh prefers fund 40 to 21, and Ireland is tied with both at 30.
Funds (or fund) describes the type of transfer, and together they form a compound noun. See the linked Cambridge and Dictionary.com definitions above, again ignoring the electronic portions. This noun is countable, but the pluralization applies to transfer. For example:
I processed seventeen funds transfers today.
Regardless of whether fund or funds is the term of choice, it should not be changed based on the amount of money being transferred, because the term never actually specifies a particular quantity of currency. The source or intended purpose of the money is also irrelevant, for the same reason: the term means nothing more than a simple movement of an unspecified quantity of money from one storage space to another.