Jordan is a key Arab opponent to the wall despite its peace treaty with Israel.
Besides Indonesia, the world's biggest Muslim country, and Malaysia, two other countries, Bangladesh and Cuba, are scheduled to speak out against the barrier on Tuesday.
The court in The Hague opened three days of hearings on Monday into the legality of the "apartheid wall". Palestinians call it a land-grab to deny them a viable state, while Israel says it needs to keep out Palestinian human bombers.
Israel has stayed away from the hearings, disputing the right of the International Court of Justice to pronounce on what it sees as a political case.
The United States and European Union have shunned the hearings despite criticising the route taken by the wall. They say the court's involvement could harm Middle East peacemaking efforts.
"The wall is indefensible as a matter of law"
UN Ambassador, Saudi Arabia
The court's ruling will not be binding, but it could influence world opinion and the Palestinians hope it could pave the way for international sanctions against Israel.
"The wall is indefensible as a matter of law," Saudi Arabia's UN Ambassador, Fawzi Shobokshi, testified on Monday.
The Hague hearings stem from a Palestinian request, backed by the UN General Assembly, to decide whether Israel is legally obliged to tear down the barrier.
Israel has built about 180km of the planned 730km long bulwark.
Palestinians say the barrier flouts international law because it absorbs chunks of occupied land and causes hardship.
They want the wall dismantled or shifted to follow Israel's boundary with the West Bank before the area was occupied along with Gaza in the 1967 Middle East war.
Israeli troops fired tear gas at thousands of Palestinians in the West Bank who held Day of Rage protests on Monday. Both sides held rallies in The Hague to press their cases.
A decision by the court could take several months.